Welcome,
You dont mention what kind of music you play.
For me Rectifiers work best in the middle around noon on the controls. Mids I tend to scoop some, of course it tells you this in the manual.
I lean toward vintage sounds cause when you push the modern channel there is just to much volume difference, and I wind up turning the master down in the 9 oclcock range and these amps for me just dont work well there.
I play hard rock cover songs, I have channel one on Clean, master wide open, gain around 9 oclock, Im not sure on the eq. My second channel is in the Raw mode master around 2 oclock gain around noon, then the 3rd channel in the vintage mode, master around noon, gain about 2 oclock. I use the loop as an attenuator, it stays around noon, solo control around 1 oclock. Im currently using a Triple Rec with 2 tubes pulled in the spongy mode. I also have a Weber Mass attenuator for quiet practice and gigs where I have to turn it down.
Rectifiers are great amps, Ive had 4 altogether now, and oh yeah recently added a Roadster Combo which is a Dual Rec at heart. The tones are in there you just have to dig for them, be careful with the bass control, whenever someone wants to play it the first thing they want to do is turn the bass way up and the treble and scoop it, it sounds real mushy to me when you do that.
Good Luck and have fun with your new amp.